Impeller blade for centrifugal fan and manufacturing method thereof

ABSTRACT

A fan blade made of a solid extruded aluminum alloy having certain cross-section shapes. Also provided is a method of producing fan blade, which includes heating a portion of a stock aluminum alloy material and pushing it through an extrusion die having an aperture while drawing the extruded portion of the material. The aperture can be designed or configured so that the extruded material has a cross section suitable to be used as an impeller blade.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. provisional application No.62/800,488, filed Feb. 2, 2019, the disclosure of which is incorporatedby reference in its entirety.

TECHNICAL FIELD

The invention relates to the technical field of a centrifugal fan, andin particular, to structure and manufacture of an impeller blade for acentrifugal fan.

BACKGROUND

Centrifugal fan assemblies include a plurality of impeller bladespositioned in a scroll-shaped housing or volute. The housing can includean inlet through which air is drawn by the fan blades, and an outletthrough which pressurized air is discharged. The plurality of bladespressurize and accelerate an incoming axial airflow, and discharge theair into a scroll portion of the housing in a substantial radialdirection. The blades may be attached to a hub fixed on a rotating shaftof an electric motor, or mounted on an outer periphery of a wheel thatrotates about such a hub.

Currently in the commercial or industrial centrifugal fans, impellerblades are usually made of metal materials, such as a ferrous metal(e.g., alloy structural steel sheet such as Q235), aluminum alloy sheet,and stainless steel. The choice of materials can depend on therequirements of specific applications and the environment where the fanis used.

The traditional fan manufacture creates a large amount of pollution andposes challenges for waste disposal. With the increased pressure by thegovernment and public for more efficient manufacture of a variety ofindustrial products, there is higher demand for environment-friendlydesign and manufacture of commercial and industrial fans. For example,the industry calls for more sophisticated and lightweight design ofimpellers. The industry must upgrade the design standards andmanufacturing levels.

As shown in FIG. 1 and FIG. 2, the centrifugal fan blade of the priorart is typically manufactured by punching, which results in sharp edgesof the impeller blade. Such sharp edges cause the impeller blades tovibrate and generate noise as well as create eddy currents, reducingtheir service life and lowering the energy use efficiency.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an impeller blade fora centrifugal fan with reduced wind resistance, eddy currents, andvibration during use of the blades, thereby reducing the possibility ofnoise generation and prolonging the service life of the impeller blades.

A further object of the present invention is to provide a method formanufacturing an impeller blade for a centrifugal fan by hot drawing astocking material through a die with particular shapes and cold workinghardening of the outer surface of a blade, which produces a blade withhigh surface hardness and excellent overall strength and rigidity withimproved wear resistance.

In one aspect, a fan blade made of an extruded aluminum alloy isprovided. The fan blade has a width direction and a uniform and solidcross section perpendicular to the width direction. The cross-sectionhas two major opposing sides, a first lateral end, and a second lateralend. The two opposing sides are both smooth curves generally, andtogether defining a thickness therebetween. In some embodiments, the twomajor opposing sides curving to opposing directions. In someembodiments, the two major opposing sides curving to a same direction,and wherein the thickness gradually increases from the first lateral endto the second lateral end. In some embodiments, the first end has aradius of about 1 mm. In certain of these embodiments, the second endhas an elliptical shape. In some embodiments, the second end has amaximum thickness of between about 3 mm to about 8 mm.

In another aspect, the present disclosure provides a centrifugal fanassembly comprising at least one mounting disc having a center and aradius; and a plurality of fan blades each defined herein which aremounted on the at least one mounting disc. In some embodiments, theplurality of fan blades are arranged radially symmetrically with respectto the center of at least one mounting disc. In some embodiments, all ofthe plurality of fan blades are arranged with the first end positionedproximal to the center of the at least one mounting disc and the secondend positioned distal to the center of the at least one mounting disc,and wherein the two major opposing sides of all of the plurality of fanblades are curving to a same rotational direction. In some embodiments,the centrifugal fan further includes an electrical motor operativelycoupled with the at least one mounting disc, the electrical motorconfigured to rotate in a direction such that each of the plurality offan blades are forward-curved.

In another aspect, a method for producing an extruded material isprovided. The method comprises: positioning a stock of a metal alloymaterial such that a first end of the metal alloy material is proximatean extrusion die, the extrusion die having an aperture on an end face;heating at least a portion of the stock of the metal alloy materialproximate the die to soften the portion of the metal alloy material;pushing the softened portion of the stock of the metal alloy materialthrough aperture along a forward direction such that a portion of themetal alloy material is extruded out of the aperture; and drawing theportion of the metal alloy material that has been extruded out of theaperture along the forward direction, thereby producing an extrudedmetal alloy material having a cross section having substantially theshape of the aperture of the extrusion die.

In some embodiments, the metal alloy material comprises aluminum alloy.In some embodiments, the method further comprises cutting the extrudedmaterial into a plurality of pieces or segments along a directionperpendicular to the forward direction of the extrusion.

In some embodiments, the aperture has a cross-section shape comprisingtwo major opposing sides defining a thickness therebetween, the twomajor opposing sides both curving in the same direction, wherein one ofthe sides has a length greater than the other of the sides. In someembodiments. In some of these embodiments, the thickness can graduallyincrease from the first lateral end to the second lateral end.

In some embodiments, wherein the aperture has a shape comprising twomajor opposing sides curving in opposite directions.

The present disclosure also provides an extruded metal alloy material oraluminum alloy material made by the method described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be understood that the drawings are intended to illustratecertain features of certain embodiments of the present invention and arenot necessarily drawn to scale.

FIG. 1 is a depiction of a cross section of a fan blade of prior art.

FIG. 2 is another depiction of a cross section of a fan blade of priorart.

FIG. 3 is an example cross section profile of a fan blade according tosome embodiments of the present invention.

FIG. 4 is another example cross section profile of a fan blade accordingto some embodiments of the present invention.

FIG. 5A is another example cross section profile of a fan bladeaccording to some embodiments of the present invention.

FIG. 5B is a fan blade having a cross section shown in FIG. 5A accordingto some embodiments of the present invention.

FIG. 6A is front view of an extrusion die having an aperture forproducing an extruded material for fabricating a fan blade according tosome embodiments the present invention.

FIG. 6B is a schematic view of an extrusion process for producing anextruded material for fabricating a fan blade according to someembodiments the present invention.

FIG. 7A is a schematic depiction of a mounting disc.

FIG. 7B is a schematic depiction of a portion of a centrifugal fanassembly including a plurality of fan blades installed on a mountingdisc.

FIG. 7C is a photograph of a partially assembled centrifugal fanassembly where a plurality of fan blades have been installed on amounting disc.

DETAILED DESCRIPTION

It should be noted that the embodiments in the present application andthe features in the embodiments may be combined with each other withoutconflict. The invention will be described in detail below with referenceto the drawings in conjunction with the embodiments.

As seen in FIGS. 1-2, in the prior art, the impeller blades 1P aretypically cut by cutting/punching, and the edges of the blade body 1Pcan be sharp structures, which tend to produce eddy currents anddisturbance to the air flow, producing vibration and instability for theblades.

As shown in FIGS. 3, 4, 5A and 5B, some example impeller blades of thepresent invention for a centrifugal fan can include: blade body 1, whereedges of the blade body 1 are all rounded transitions. In contrast toprior art impeller blades (as shown in FIGS. 1-2), the impeller bladesof the present invention include rounded or smooth transitions at theedge of the blade body. This can be accomplished through adrawing/stretching process which will be further described below. Suchsmooth transitions reduce wind resistance of the impeller blades,improves circumferential exhausting ability, reduces vibration duringthe use of the blade, thereby reducing noise generation and prolongingthe service life of the impeller blade.

In one embodiment, as shown in FIG. 3, the cross section of blade body 1can have a substantially bilaterally symmetrical shape (thus the body 1has a symmetrical arcuate curved surface), with greater thickness in themiddle, tapering on both lateral ends. This type of blade can be used inlow-power and low air pressure applications which do not require highstrength. For example, the maximum thickness of the cross section of theblade body 1 D_(M) can be about 2 to 10 mm, e.g., 5 mm, and the laterallength (or chord length) L_(C) of the blade body 1 can be from about 100to about 300 mm, or from about 100 to about 200 mm, e.g., about 180 mm.The chord height of the cross section of the blade body 1 C_(H) can beabout 10-20 mm; and the radius of the lateral edge of the blade body 1can be between 0.5 and 3 mm, e.g., about 1 mm or about 2 mm. The crosssection has two major opposing sides, i.e., a top side curve 31, and abottom side curve 32, both curving toward the same direction (in otherwords, they are both convex or both concave). As shown in FIG. 3, thecontour length of the top curve is greater than that of the bottom curve32. The curves can be arc part of a circle, or can be of more complexcurves (e.g., those that can be approximated by higher powerpolynomials).

In another embodiment, as shown in FIG. 4, the blade body 1 has asymmetrical curved surface and the two major opposing sides, top sidecurve 33 and bottom side curve 34, that curve in opposing directions.The center of the blade body 1 can have a greater thickness than boththe lateral ends. For example, in some embodiments, the blade body 1 canhave a maximum thickness D_(M) of about 5 mm in the middle of the crosssection, a cross section length L_(C) of from about 100 to 300 mm, orfrom about 100 to about 200 mm, e.g., about 180 mm. The lateral sideedge radius R1 can be between 0.5 and 3 mm, e.g., about 1 mm, or about 2mm. The top side curve 33 can have a contour length greater than, equalto, or smaller than that of the bottom side curve 34.

In still another embodiment, as shown in FIG. 5A, the blade body 1 canhave an asymmetrical arcuate curved surface. This design can meet therequirements of higher precision and higher air flow speed, furtheravoiding eddy currents, ensuring that the blade body 1 does not vibrate,thereby avoiding noise, and prolonging the service life of thecentrifugal fan. In order to reduce eddy currents, the cross section ofthe blade body 1 can take a shape that is gradually enlarged from afirst lateral (or front) end to a second lateral (or rear) end. In theembodiment shown in FIG. 5A, the blade body 1 includes a rotatingwindward surface 11 and a rotating leeward surface 12, wherein thewindward surface 11 is a side of the blade body 1 that rotates againstthe wind. The rotating windward surface 11 can have a uniform arc shape,and the rotating leeward surface 12 can have a plurality of arcssmoothly joined. The plurality of circular arc transitions prevent thewind flow through the rotating leeward surface 12 from flowing towardthe rotating windward surface 11, thereby preventing the formation ofeddy currents.

In some embodiments, in order to reduce the design difficulty and thehigh process precision requirements, the rotating leeward surface 12includes two smooth transitional arc surfaces, namely a front endleeward surface 121 and a rear end leeward surface 122. The radius ofthe arc surface of the front leeward surface 121 can be similar or aboutthe same as the radius of the rotating windward surface 11 so that theair entering the axial direction of the centrifugal fan can enteradjacent centrifugal blade space more smoothly. In such a manner, a highworking efficiency of the centrifugal fan can be attained.

As the front end leeward surface 121 extends toward the rear end leewardsurface 122, it also further deviates away from the rotating windwardsurface 11. The rear end is larger in cross section, ensuring thestrength of the blade to satisfy the operating needs. Also, since thecentrifugal fan structure is usually designed as a circular structure,the rear end of the centrifugal blade is often installed in thecircumferential direction of the circular structure (that is, the endthat is distal from the central rotating axis). This difference indimensions between the front end and rear end of the blade also helpsreduce the space between adjacent centrifugal blades toward thecircumference. Excessive space between adjacent blades can result in theformation of eddy currents, which in turn lead to noise and vibrationdefects.

In order to avoid excessive increase in the size of the curved blade,and to ensure that the wind flow can flow on a relatively gentle arcsurface, the radius of the rear leeward surface 122 is larger than theradius of the front leeward surface 121, and the rear leeward surface122 is extended away from the end of the front leeward surface 121.Preferably, the blade body 1 further includes a front end portion 101and a rear end portion 102. In order to make the wind flow more uniformand smoother, the upper and lower sides of the front end portion 101smoothly transition from the rotating windward surface 11 and the frontend leeward surface 121, respectively. The cross section of the rear endsurface 102 can have an elliptical shape, and the upper and lower sidesof the rear end surface 102 smoothly transition with the rotatingwindward surface 11 and the rear end leeward surface 122, respectively.The maximum thickness of the rear end surface 102 D_(R) (which can beconsidered the “height” or length along the minor axis of an ellipseapproximating the rear end cross section shape) can be about from 3 mmto about 8 mm, for example, about 5 mm. The front end portion 101 canhave a radius from 0.5 mm to 3 mm, e.g., about 1 mm, or about 2 mm. Thecross section length L_(C) can be about 100 to about 300 mm. In someembodiments, the cross section length L_(C) of the fan blade as shown inFIG. 5A can be about 8¾ inches (or 222.2 mm), D_(R) can be about ⅛ inch(or 3.2 mm), and the radius of the front end portion 101 can be about1/32 inch (or about 0.8 mm).

FIG. 5B illustrates the relationship between the cross section Sc of ablade and its width direction which is perpendicular to the crosssection Sc. Along the width direction, the shape of the cross section Scremains the same (or uniform).

In another aspect of the invention, a process for producing an extrudedmaterial, e.g., a metal alloy, is provided. The extruded material cantake a sheet-like shape, with cross section shape similar to thosedepicted in FIGS. 3, 4, and 5A/5B. The process can be a continuousprocess and the extruded material can be cut into pieces to makeplurality of impeller blades of desired sizes.

An example extrusion die 60 useful for the process is illustrated inFIG. 6A. In this illustration, the aperture 65 on the front end face 60Atakes the shape similar to the cross section shape of a blade depictedin FIG. 5A. The description of the geometry of the cross-section profileof the blade can be equally applicable to the aperture 65. In otherembodiments, the aperture 65 can take the cross section shape of theblades as illustrated in FIGS. 3 and 4 (the description of geometrythereof are likewise applicable to that of the aperture in suchinstances).

As further illustrated in FIG. 6B, the extrusion process can includepositioning a stock (e.g., a rod) of a metal alloy material 62 such thata first end of the metal alloy material is proximate the extrusion die60. At least a portion of the stock of the metal alloy materialproximate the die can be heated to soften the portion of the metal alloymaterial. In an example, an aluminum alloy rod stock material with acomposition containing about 0.5% Si by weight (wt), about 0.8 wt % Mg,about 0.7 wt % Fe, about 0.2 wt % Cu, about 0.15 wt % Mn, and 0.25 wt %Zn (the remainder being Aluminum) is heated to between about 550° C. and590° C. for softening before passing the die. The softened portion ofthe stock of the metal alloy material is pushed through aperture 65 inthe extrusion die 60 in a forward direction, e.g., by an upper roller 67and a lower roller 68, or other pushing mechanism of the extrusionmachinery, such that a portion of the metal alloy material is extrudedout of the aperture 65. The portion of the metal alloy material that hasbeen extruded out of the aperture and exposed is drawn along the forwarddirection (e.g., by using a damper movable along the forward direction)without heating, e.g., at room temperature, thereby producing anextruded metal alloy material having a cross section havingsubstantially the shape of the aperture of the extrusion die. Thedrawing helps produce extruded metal alloy material with smooth/roundededges, as well as facilitate crystallization of the metal material,especially on the surface of the extruded material, which improves thesurface hardness and wear resistance of the extruded material. Thepushing and drawing may be performed simultaneously, and the speed ofpushing of the stock material and drawing of the extruded material canbe coordinated/adjusted to produce a drawn sheet of desired dimension,geometry and properties. The extruded metal material can be cut along adirection perpendicular to the forward direction, thus producing aplurality of pieces each suitable to be used as an impeller blade asdescribed herein.

A plurality of fan blades 1 described herein can be integrated into acentrifugal fan assembly. The blades can be installed on at least onemounting disc 710 (or two or more mounting discs, as needed) having arotational center 715, as shown in FIG. 7A. FIG. 7B shows a side view ofthe plurality of blades 720 (similar to what has been shown in FIG. 5A)installed near the outer circumference of the mounting disc 710. Thecentrifugal fan assembly can further include an electric motoroperatively coupled with the mounting disc (or mounting discs), theelectrical motor configured to rotate in a direction such that each ofthe plurality of fan blades are deemed forward-curved, as shown in FIG.7B. FIG. 7C is a photograph of a partly assembled fan assembly where aplurality of fan blades have been installed on a mounting disc.

It is to be noted that the terminology used herein is for the purpose ofdescribing particular embodiments, and is not intended to limit theexemplary embodiments. As used herein, the singular forms are alsointended to include the plural, unless the context clearly indicatesotherwise, and it is also understood that when the terms “include”and/or “include” are used in the specification.

The term “about” as used with reference to a certain given value orquantity herein means a range of up to 25% deviation from (greater orsmaller than) the given value.

While illustrative embodiments of the invention have been disclosedherein, numerous modifications and other embodiments may be devised bythose skilled in the art in accordance with the invention. For example,the various features depicted and described in the embodiments hereincan be altered or combined to obtain desired scaffold characteristics inaccordance with the invention. Therefore, it will be understood that theappended claims are intended to include such modifications andembodiments, which are within the spirit and scope of the presentinvention.

1. A fan blade made of an extruded aluminum alloy, the fan blade havinga width direction and a uniform and solid cross section perpendicular tothe width direction, the cross-section having two major opposing sides,a first lateral end, and a second lateral end, the two opposing sidesbeing both smooth curves generally, the two opposing sides defining athickness therebetween.
 2. The fan blade of claim 1, wherein the twomajor opposing sides curving to opposing directions.
 3. The fan blade ofclaim 1, wherein the two major opposing sides curving to a samedirection, and wherein the thickness gradually increases from the firstlateral end to the second lateral end.
 4. The fan blade of claim 3,wherein the first end has a radius of about 1 mm.
 5. The fan blade ofclaim 3, wherein the second end has an elliptical shape.
 6. The fanblade of claim 5, wherein the second end has a thickness of betweenabout 3 mm to about 8 mm.
 7. A centrifugal fan assembly comprising: atleast one mounting disc having a center and a radius; and a plurality offan blades each defined according to claim 3 mounted on the at least onemounting disc.
 8. The centrifugal fan assembly of claim 7, wherein theplurality of fan blades are arranged radially symmetrically with respectto the center of the at least one mounting disc.
 9. The centrifugal fanassembly of claim 8, wherein each of the plurality of fan blades arearranged with the first end positioned proximal to the center of the atleast one mounting disc and the second end positioned distal to thecenter of the at least one mounting disc, and wherein the two majoropposing sides of all of the plurality of fan blades are curving to thesame rotational direction.
 10. The centrifugal fan assembly of claim 9,further comprising an electrical motor operatively coupled with the atleast one mounting disc, the electrical motor configured to rotate in adirection such that each of the plurality of fan blades areforward-curved.
 11. A method for producing an extruded material,comprising: positioning a stock of a metal alloy material such that afirst end of the metal alloy material is proximate an extrusion die, theextrusion die having an aperture on an end face; heating at least aportion of the stock of the metal alloy material proximate the die tosoften the portion of the metal alloy material; pushing the softenportion of the stock of the metal alloy material through aperture alonga forward direction such that a portion of the metal alloy material isextruded out of the aperture; and drawing the portion of the metal alloymaterial that has been extruded out of the aperture along the forwarddirection, thereby producing an extruded metal alloy material having across section having substantially the shape of the aperture of theextrusion die.
 12. The method of claim 11, wherein the metal alloymaterial comprises aluminum alloy.
 13. The method of claim 11, furthercomprising cutting the extruded material into a plurality of piecesalong a direction perpendicular to the forward direction of theextrusion.
 14. The method of claim 11, wherein the aperture has across-section shape comprising two major opposing sides defining athickness therebetween, the two major opposing sides both curving in thesame direction, wherein one of the sides has a length greater than theother of the sides.
 15. The method of claim 14, wherein the thicknessgradually increases from the first lateral end to the second lateralend.
 16. The method of claim 11, wherein the aperture has a shapecomprising two major opposing sides curving in opposite directions. 17.An extruded metal alloy material or aluminum alloy material made by themethod of claim 11.